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[ ESA 3- Infection and Immunity > Allergies > Flashcards

Allergies Flashcards

1
Q

What does the term hypersensitivity describe?

A

The antigen specific responses that are either inappropriate or excessive, and result in harm to host

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2
Q

What mechanisms underlie the hypersensitivity immune responses?

A

Those employed by the host to fight infections

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3
Q

What are the common features of hypersensitivity responses?

A

Sensitisation phase

Effector phase

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4
Q

What happens in the sensitisation phase of a hypersensitivity response?

A

First encounter with antigen

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5
Q

What happens in the effector phase of a hypersensitivity response?

A

Clinical pathology upon re-exposure to same antigen

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6
Q

What are the types of hypersensitivity reactions?

A

Type I, or immediate
Type II, or antibody mediated
Type III, or immune complex mediated
Type IV, or cell mediated

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7
Q

How quick is the onset of type I hypersensitivity reactions?

A

<30 minutes

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8
Q

What are type I hypersensitivity reactions also known as?

A

Allergies

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9
Q

What are type I hypersensitivity reactions a response to?

A

Environmental non-infectious agents (allergens)

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10
Q

What molecule do type I hypersensitivity reactions involve?

A

IgE

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11
Q

When is the onset of type II hypersensitivity reactions?

A

5-12hrs

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12
Q

What are type II hypersensitivity reactions a response to?

A

Non-soluble tissue antigens

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13
Q

What molecule do type II hypersensitivity reactions involve?

A

IgG

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14
Q

When is the onset of type III hypersensitivity reactions?

A

3-8hrs

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15
Q

What are type III hypersensitivity reactions a response to?

A

Soluble antigens

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16
Q

When is the onset of type IV hypersensitivity reactions?

A

24-48hrs

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17
Q

What is a type IV hypersensitivity reaction a response to?

A

Environmental infectious agents and self antigens

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18
Q

What kind of diseases are type IV hypersensitivity reactions?

A

Autoimmune diseases

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19
Q

What is happening to the worldwide prevalence of allergies?

A

It is increasing

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20
Q

How does the incidence of allergy in the UK compare to other countries?

A

It is in the top 3 countries with the highest incidence of allergy

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21
Q

What % of children in the UK have an allergy?

A

> 50%

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22
Q

How many <45 year olds have 2 or more allergies in the UK?

A

13 million

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23
Q

What proportion of children have a peanut allergy in the UK?

A

1 in 50

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24
Q

How much do allergies cost per year in primary care in the UK?

A

£900 million

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25
What is the development of allergy thought to be affected by?
A mixture of genetics and environmental factors
26
What phenotype often present as non-allergic?
TH1
27
What phenotype often presents as allergic?
TH2
28
How is geographical location related to allergy?
Those from developing countries tend to have less allergies, and those from westernised countries tend to have more allergies
29
Why do people from developing countries tend to have less allergies?
``` Large family sizes Rural homes, lifestock Intestinal microflora variable/transient Low antibiotic use High helminths burden Poor sanitation, high orofecal burden ```
30
Why do those from westernised countries tend to have more allergies?
``` Small family size Affluent, urban homes Intestinal microflora stable High antibiotic use Low or absent helminths burden Good sanitation, low orofecal burden ```
31
What are the common allergies?
``` House dust mite, cockroaches Animals Tree and grass pollen Insect venom Medicines Chemicals Foods ```
32
What animals are people commonly allergic too?
Domestic pets such as cats and dogs
33
What insect venoms are people commonly allergic too?
Those contained in wasp and bee stings
34
Give an example of medicines people are commonly allergic too
The antibiotic penicillin
35
Give an example of a chemical people are often allergic too
Latex
36
What foods can people be allergic too?
``` Milk Eggs Wheat Peanuts Tree nuts Seafood ```
37
What should be considered with people with allergies?
People with allergies can often have cross-reactions with other associated allergens
38
What are hypersensitivity reactions caused by?
Activation of mast cells through IgE dependant mechanisms
39
What is the result of activation of mast cells in hypersensitivity?
These activated mast cells then release chemical mediators
40
What is the most important chemical mediator in hypersensitivity reactions?
Histamine
41
What are the classes of chemical mediators in hypersensitivity reactions?
``` Enzymes Toxic mediator Cytokine Chemokine Lipid mediator ```
42
Give 4 examples of enzyme chemical mediators in hypersensitivity reactions
Tryptase Chymase Cathpepsin G Carboxypeptidase
43
What are the biological effects of enzyme chemical mediators in hypersensitivity reactions?
Remodel connective tissue matrix
44
Give two examples of toxic mediators in hypersensitivity reactions
Histamine | Heparin
45
What are the biological effects of toxic mediators in hypersensitivity reactions
Toxic to parasites Increase vascular permeability Cause smooth muscle contraction
46
Give 6 cytokine chemical mediators in hypersensitivity reactions
``` IL-4 IL-13 IL-3 IL-5 GM-CSF TNF-alpha ```
47
What are the biological effects of IL-4 and IL-13 in hypersensitivity reactions?
Stimulate and amplify TH2 cell response
48
What are the biological effects of IL-3, IL-5, and GM-CSF in hypersensitivity reactions?
Promote eosinophil production and activation
49
Where does the TNF-alpha in hypersensitivity reactions come from?
Some stored preformed in granules
50
What are the biological effects of TNF-alpha in hypersensitivity reactions?
Promotes inflammation Stimulates cytokine production by many cell types Activates endothelium
51
What chemokine chemical mediator is released in hypersensitivity reactions?
CCL3 (MIP-1alpha)
52
What are the biological effects of chemokines in hypersensitivity reactions?
Attracts monocytes, macrophages, and neutrophils
53
Give 4 lipid mediators in hypersensitivity reactions
Leukotrienes C4, D4, E4 | Platelet-activating factor
54
What are the biological effects of leukotrienes in hypersensitivity reactions?
Cause smooth contraction Increase vascular permeability Stimulate mucus secretion
55
What are the biological effects of platelet-activating factor in hypersensitivity reactions?
Attracts leukocytes Amplifies production of lipid mediators Activates neutrophils, eosinophils, and platelets
56
What does an initial exposure to an allergen cause?
Plasma cells to create an antigen-specific IgE
57
What happens once an antigen-specific IgE has been produced?
It binds to mast cells to sensitise it to the specific antigen (allergen)
58
What does second exposure to an allergen cause?
Cross-linking of the IgE molecules on the surface of the mast cell
59
What does cross linking of IgE molecules on the mast cell trigger?
The release of granule contents, including histamine and chemokines, and synthesis of new mediators; leukotrienes and prostaglandins
60
What does the release of granule contents from mast cells result in?
A number of physiological changes, such as; Increased vascular permeability Vasodilation Bronchoconstriction
61
How is an allergic reaction diagnosed?
Blood/serum levels of mast cell products
62
Where can the effects of an allergic reaction manifest?
The epidermis | Deep dermis
63
How can the effects of allergic reaction manifest in the epidermis?
Increased vascular permeability and vasodilation results in urticaria (hives)
64
How does urticaria present?
Creates a wheal and flare type marking on the skin
65
How can the effects of an allergic reaction manifest in the deep dermis?
Increased vascular permeability and vasodilation results in angiodema of the lips, eye, tongue, and upper respiratory tract
66
What is the problem with the manifestation of allergic reaction in the deep dermis?
It can carry the risk of suffocation if in the respiratory tract
67
What can systemic activation of mst cells result in?
Anaphylaxis
68
How serious is anaphylaxis?
Medical emergency- death if not treated
69
What happens in anaphylaxis?
Increased vascular permeability leads to hypotension and cardiovascular collapse Generalised urticaria and angiodema Bronchoconstriction leads to breathing problems
70
How many deaths did anaphylaxis result in between 1992 and 2001?
Over 200 but im pretty sure this isnt going to be in the exam so its a pointless fact
71
When should anaphylaxis be treated?
Immediately
72
How should anaphylaxis be treated?
Intramuscular adrenaline
73
What is the effect of intramuscular adrenaline in anaphylaxis?
Reverses peripheral vasodilation and reduces oedema Alleviates hypotension Reverses airway obstruction/bronchospasm Increases force of myocardial contraction Inhibits mast cell activation
74
Why is adrenaline said to be a time-saver rather than a life-saver in anaphylaxis?
Reactivation can re-occur in 20% of patients without re-exposure to the antigen
75
What may be required with adrenaline in anaphylaxis?
Multiple doses
76
What is required with adrenaline in anaphylaxis?
Proper use of the epipen
77
What is it important to do after treatment with adrenaline in anaphylaxis?
Continue to monitor pulse, BP, ECG, and O2 sats
78
What factors are considered in a diagnosis of allergy?
Clinical history Blood tests Skin prick tests Challenge tests
79
What clinical history is considered in allergy?
Atopy Allergens Seasonalities Route of exposure
80
What blood tests are done in diagnosis of allergy?
Serum allergen-specific IgE | Serum mast cell tryptase, histamine (systemic granulation)
81
What allergens are skin prick tests done for?
Range of allergens
82
What is being looked for in skin prick tests?
Wheat and flare reaction of >3mm
83
What do skin prick tests need?
Trained personnel
84
When is a challenge test done?
Food and drug allergy
85
What is the problem with challenge tests?
Slight risk of anaphylaxis on highly sensitised patients
86
How is an allergy managed?
``` Allergen avoidance/elimination Education Medic alert information Drugs Allergen desensitisation ```
87
How can allergens be avoided/eliminated?
Read food levels House dust mite avoidance Avoid high risk situations
88
What education is given in management of allergy?
Parents to recognise symptoms Patients to use epipen Call emegency devices when epipen is used Schools and social activities
89
What drugs can be given in the management of allergy?
Antihistamines Corticosteroids Anti-IgE IgG Anaphylaxis
90
What should be given in antihistamine prevention?
Alternating sedating/non-sedating forms
91
How can corticosteroids be administered in allergy management?
Topical | Systemic
92
Give an example of an anti-IgE IgG drug
Omalizumab
93
What does allergen desensitisation involve?
Administration of increasing doses of allergen extracts over a period of years
94
When is allergen desensitisation used?
In patients with high risk of systemic attack
95
Under what conditions must allergen desensitisation take place?
In a specialist hospital based unit with resuscitation equipment

[ ESA 3- Infection and Immunity (15 decks)

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